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first I want to introduce myself. My name is Joerg (it is a German form from "George"), living in the middle of Germany. I am a new CLK-owner and found this forum by searching for hints, which help to get my soft top working again.
Something about my background. I am a mechanical engineer and like to understand the working of mechanism. And the soft top mechanism is a very interesting thing.
I know, there are many threats about soft top problems and I hope, I read all but now there are more and more questions in my head. Perhaps I find the solution and may add a "how to" to help other people in this case.
I am sorry, but my English is not good, but I hope I can describe my problems in the right way.
I bought the car with a faulty roof, thinking it is easy to fix. This may have been a fault but it is a challenge.
A short description of the roof opening process in my car:
- Turning key to position 2
- Use handle and open the roof front part -> roof switch (S84) lights constantly red, windows are going down
- Pulling the roof switch -> hydraulic starts and headrests are going down
- When headrests are down -> you see the fabric bow is pulled down a little bit.
Then the process is stopping, nothing happens further on. The hydraulic keeps on running as long I pull the switch.
When I press the switch, I get a short signal (may be the "finish closing signal") and when you lock the front roof part with the handle, the switch light goes out. When you press the switch longer, the windows and the headrest are going up.
I put my smartphone in the trunk and made a video of the fabric bow lock. There you can see clearly, that the hydraulic cylinder tries to pull the piston backwards (try to close the lock).
When I have a look at the hydraulic wiring (I found only a relatively bad picture of the wiring), you can see that the locks for fabric bow and compartment cover are activated automatically, when the hydraulic pump starts.
I have checked the switches of both locks and everything is working.
Have you any idea, where to look further? Does the N52 controller check all signals and it may be an other switch?
To check the other switches, I have to remove the side panels in the rear. How do I this work? I have no WIS to check it.
Sorry,
I forgot something to tell. I have changed the hydraulic tubes at the fabric bow lock cylinder to see what happens. When you pull the switch S84 the fabric bow is unlocked but the switch is blinking in 1 second mode. It indicates, that there is a fault.
The fault is not a changed tube wiring to this cylinder.
Hello Joerg and welcome to the to the W208/A208 family.
You have already done an excellent job in troubleshooting and diagnosing your power soft top problem. Your detailed problem description and video was very helpful.
For general informational purposes, I'm enclosing some documentation.
When the lamp on the main switch remains on, or flashes, the purpose is to provide basic fault information and the details are explained an enclosed thumbnail.
You'll also find a N52 controller functional block diagram. Basically, as the power roof operates the controller evaluates a series of inputs, from various position/limit switches/CANBus upon which various outputs activate, such as the hydraulic pump, valve solenoids, rear window motors and CANBus modules.
When the rear bow is not properly locked or unlocked, power roof operation will not progress.
When the soft top bow does not close or only closes slowly, the possible cause can be the soft top compartment "open" switch (S84/5), fabric bow "lower" valve (Y55y9), leaking hydraulic cylinder, raise/lower soft top bow (left and/or right).
When the soft top does not open or only raises slowly, the possible cause can be the soft top fabric bow up/down limit switch (S84/15), power top "open" (Y56/2y1), a leaking hydraulic cylinder, open/close soft top (left or/and right).
Another enclosed thumbnail, details the operation of the rear bow lock cylinder. With age, a very common problem with the cabriolet, has been with the soft top compartment cover and rear bow lock cylinder internal/external seal failures. In your video, there does not seem to be external leak at this time, however, note that the cylinder is differential (2 way action) and there may be an internal leak.
However, there was another clue in your video. Specifically, when the cylinder tried to activate the lock, the noise generated was not normal (e.g. there should only be a pop, as the strike releases). While it's not common, several owners have found a piece in the linkage mechanism, had moved out of position or jammed. IMHO, I would look there as your next step.
Should your issue turn out to be a leaking cylinder, a forum sponsor, Top Hydraulics, provides excellent and reasonable global rebuild services. Their link is:
Also, note the 2 links provided on the above link, that provide comprehensive DIY repair tutorials.
Lastly, your profile did not indicate your model year. In late 2000 or early 2001, Mercedes updated a few of the power roof components and I believe the rear bow lock mechanism was one of them. As a result, the N52 controller, rear bow lock are not compatible between early and late production cars.
Last edited by Serndipity; 10-09-2016 at 11:57 AM.
thank you for your detailed reply. Your documents are well known and I have downloaded them some time ago.
Of course I know tophydraulicsinc.com. A very interesting site and a gold mine for roof problems.
Yesterday I stripped the half car to get access to all parts of the roof. I can exclude external and internal leaking of the hydraulic cylinders, because the two lock cylinders are new, bought by the former owner, because they were leaking. I made another video from the compartment lock and it shows the same behavior. When the pump starts, the cylinder tries to close it more.
But this is explainable, when you have a look at the hydraulic plan, posted in this forum. The two lock cylinders starts to close their locks, when pump starts and this behavior is shown in the videos.
I can not understand the intention of this wiring, because to open the locks, there is still pressure on the plunger side, when the solenoid valves open the hydraulic gate to the piston side. Because of the principle of differential cylinders, they will move and open the locks.
I think, this is a kind of security item to keep the lock cylinders plunger sides under pressure, when the pump is running.
I am very astonished to have problems to open or close the fabric bow manually. When I open the bypass valve for manual soft top movement, it is nearly impossible to open the compartment lock with the special tool. You need the strength of an bear to open it. And this seems not to be normal.
This depends on the fact, that the hydraulic fluid on the plunger side of the compartment lock cylinder is not able to go to the reservoir. There is a check valve in the line, which closes the way. Moving the lock is easy, when the hydraulic hose is released.
I am now on the way, that there may be a problem with the hydraulic unit.
I look for more information and keep you up to date.
If someone need pictures from the car technic in the back, please ask. Im am now driving without panning, backseat and carpets.
In the 2nd video, the buzzing sound, when activating the case cover lock, is also not normal. Also, after just turning back the pressure relief screw, manually unlocking it should be easy.
Another thought would be that, prior to the previous owner replacing both the rear bow and case cover leaking cylinders, continued operation may have caused another problem.
Specifically, when the cylinder seals fail, they become brittle and deteriorate. It is possible that crumbled particles can then block pump valves.
First and second video are in the same time. When I press my S84 button, both lock cylinders work in the shown way (Of course, they are pulling only as long as I press the button. On the video, I did it twice).
It is a good idea to check the hydraulic unit for crumbles. This may be worth to look after.
Today I was lucky to catch a hydraulic unit with the same part number as mine with a moderate price. I want to put one on stock. Now I am able to change the hydraulic units and will see, what happens.
I will keep you up to date.
I installed an other used hydraulic pump and tested the roof. But it was the same problem. After lowering the roll bar nothing was going on.
Then I decided to check all the limit switches from the roof at the N52 controller. I removed the battery ground cable to prevent from current problems. Then I unplugged the multi cable connector from the N52. I made a list, which switches have to be laid on ground, when the roof is in the closed position. For this I used the wiring diagram in this forum.
Then I checked the resistance between the connector plug of a switch and ground. And there I found, that the lower roll bar switch gave no signal.
There were two possibilities: a broken cable or a broken switch.
I removed the back seat and checked the switch at its plug. Nothing. It seemed the cable was ok.
I removed the switch and tested it by hand. And it works. But there are two very thin spacers looking like washers between the switch and the switch threat at the roll bar guiding. I removed one spacer and now it works perfect! It seems that after some time the roll bar guiding may be getting a little loose and does not push the plunger of the switch deep enough. Small problem but big effect.
03 SL Kleemann, 97 SL320 pano top, 95 Lorinser E320 Cabrio, Ferrari 360, Tesla X
Roll bar down switch was the problem
Hello Joerg (sigi_rs), belated welcome to the forum, and congratulations on solving the problem! This will certainly be helpful to others in the future.
Just to summarize and clarify for future readers, the problem with your CLK top not working was with the "roll bar down" switch not getting triggered. The computer will not move the top before it has a signal that the roll bar is down. Seeing the rear bow (the soft top section with the rear window in it) pull down a little, as well as the case cover, was a distraction. Any time the pump runs, the two locking cylinders 1298001672 (rear bow lock cylinder in rear bow lock p/n 1247700426) and 1298000072 (case cover locking cylinder in case cover lock p/n 1247500684 or case cover lock 2087500984) get pressurized on the shaft side. This makes the locks pull down or close. For completeness: the same cylinders get pressurized on both sides to open or unlatch. If there is pressure on both sides, then the shafts in these cylinders will extend, because there is more net force pushing up than pulling down. When you reversed the hoses on one of the latches, the latch actually opened, but this was illogical to the soft top controller, because the lock was not supposed to unlatch before the roll bar gave the "fully retracted" signal.
hi
as per your advice I did the code checking. It blinks 21 times. I found what it means, but don't know what to do next. Does it mean that switch is bad or something else?
I really appreciate your response to my other issues. I'm not going to do the door dome lights. It's too much of a hassle. I'll check light switch for any alterations.
One more thing that is propably a little more serious: cold start issue. After overnight in the garage it has rough idle. When it's warmed up after 2-3 min it works like a clock. It happens every time when it's longer then an hour. It seems the engine needs to reach certain temperature to stabilize.
Also there is strong smell of fumes.
I changed spark plugs, rotors, rotor caps, and oxygen sensor. What would be the next step?
recently I'm reading a lot of different posts and I see your name very often. You must be genius mechanic and in love with this brand.
Thank You
Hello, my rollbar control button don't works, when i push it, it operates passenger door glass. (headrest stays in upper position and i think that's why my soft top stopped working)
+ the glass button does nothing at all. any ideas ? or which module controls this operations ? thanks
10-09-2016, 04:53 AM
but now there are more and more questions in my head. Perhaps I find the solution and may add a "how to" to help other people in this case.
But there are two very thin spacers looking like washers between the switch and the switch threat at the roll bar guiding. I removed one spacer and now it works perfect! It seems that after some time the roll bar guiding may be getting a little loose and does not push the plunger of the switch deep enough. Small problem but big effect.
